Correspondence of SubHalo ID between subhalo catalog and circularity catalog
Kevin Andrade
19 Nov '22
I'm trying to create a subset of subhalos that are above a mass threshold and likely to be lensing elliptical (non-disk) galaxies. I'm looking at TNG50-1, at redshift 0. My approach has been to query the subhalo catalog with the criteria that log10 total mass > 12.5, which results in 64 subhalos. Their IDs are [0, 63864, 96762, 117250, 143880, 167392,..., 452031]. Next, I load the circularity data from http://www.tng-project.org/api/TNG50-1/files/stellar_circs.hdf5, for which I see 7,904 subhalos. They have Subfind IDs: [0, 1, 2, 3, 4,..., 1060768]. So, their subfind IDs do not intersect with the subset of IDs I found in my mass-based query (except for subhalo 0). Why is that? Do the "subfind ID" fields not correspond between the two databases?
Dylan Nelson
20 Nov '22
They do intersect, as you say, but they are not the same, which is expected given that your first set of IDs is for your mass selection.
Isn't 63864, 96762, etc also in the stellar circ list? For each ID in your mass selection, you just want to find it (i.e. np.where() to find the index), so that you can get its circularity.
Kevin Andrade
20 Nov '22
Ahh, yes, I had a had a bug in my check for overlap. Thanks for responding.
I'm trying to create a subset of subhalos that are above a mass threshold and likely to be lensing elliptical (non-disk) galaxies. I'm looking at TNG50-1, at redshift 0. My approach has been to query the subhalo catalog with the criteria that log10 total mass > 12.5, which results in 64 subhalos. Their IDs are [0, 63864, 96762, 117250, 143880, 167392,..., 452031]. Next, I load the circularity data from http://www.tng-project.org/api/TNG50-1/files/stellar_circs.hdf5, for which I see 7,904 subhalos. They have Subfind IDs: [0, 1, 2, 3, 4,..., 1060768]. So, their subfind IDs do not intersect with the subset of IDs I found in my mass-based query (except for subhalo 0). Why is that? Do the "subfind ID" fields not correspond between the two databases?
They do intersect, as you say, but they are not the same, which is expected given that your first set of IDs is for your mass selection.
Isn't 63864, 96762, etc also in the stellar circ list? For each ID in your mass selection, you just want to find it (i.e. np.where() to find the index), so that you can get its circularity.
Ahh, yes, I had a had a bug in my check for overlap. Thanks for responding.